This invention relates to a paint substitute film used as substitutes for painting of exterior panels or components of an automobile or the like.
In order to improve an ornamental design of exterior components or trims, such as fenders, bumpers, hoods, wheel caps, and other plastic components, of a vehicle, spray paint is employed in most instances. However, a painting process including an operation of spraying paint requires a large facility and wide space for repeatedly performed painting and drying steps and would reduce productivity; therefore, in recent years, the use of ornamental film (hereinafter referred to as “paint substitute film”) for improving an outer appearance of a finished product has been receiving attention as serving to streamline a finishing process for the product.
A paint substitute film 101 as conventionally used, for example as shown in FIG. 4A, includes a clear coat 102, a color coat 103, and an adhesive layer 104 which are laminated one after another.
The clear coat 102 is formed using a high-transparency plastic material composed for example of polyurethane, acrylic resins, polyester resins, silicon resins, polyvinylidene fluoride (PVDF) or mixtures thereof, and serves to protect and gloss over the color coat 103, and to exert other advantageous effects. The color coat 103 is formed with metallic pigments 105 added to resinous materials having substantially the same composition as of the clear coat 102, and serves to produce a metallike effect similar to spray paint in appearance. The adhesive layer 104 serves to bond the paint substitute film 101 onto a surface of an exterior component or the like of an automobile.
When the paint substitute film 101 is bonded to the exterior component or the like, the paint substitute film 101 heated in advance under infrared irradiation from an infrared lamp or the like is formed into a shape conforming to a surface of the exterior component by an in-mold process, a vacuum forming or the like, and bonded to the exterior component using the adhesive layer 104. Upon bonding the paint substitute film 101 to the exterior component, the paint substitute film 101 is drawn so as to conform to a mold or a contoured surface of the exterior component (see FIG. 4B), while retaining a layered structure thereof as illustrated in FIG. 4A.
As shown in FIG. 4A, the metallic pigments 105 each shaped like a staple fiber or a flake are dispersed in the color coat 103 of the paint substitute film 101 in a manner that permits random orientations of the pigments 105. This composition allows rays of light incident from outside on the paint substitute film 101 to diffuse upon reflection off the metallic pigments 105, thereby providing a metallic-color appearance similar to that which is provided by spray paint.
However, when a metallic paint substitute film 101 is bonded to an exterior component having a complex (three-dimensional) shape among various exterior components of an automobile or the like, the film 101 is drawn to a large extent, partly, especially at a convexly curved area, so that disadvantages are entailed as below.
When the paint substitute film 101 is drawn upon application to the exterior component, the metallic pigments 105 randomly dispersed in the color coat 103 are made aligned with a direction parallel to a drawing direction (as indicated by an arrow in FIG. 4B). This phenomenon will hereinafter be referred to as “orientation” of the metallic pigments 105 (i.e., the pigments 105 are, in other words, oriented in a direction parallel to the drawing direction). Rays of light incident from outside on the paint substitute film 101 would strike on the metallic pigments 105 as thus oriented, but could not diffuse upon reflection off the pigments 105. Consequently, a desired metallic color cannot be produced, and thus the color of the paint substitute film 1 would disadvantageously be made different from its intended appearance.
FIG. 5 is a graph showing a characteristic curve of a relationship between a film drawing rate and a color difference, obtained from results of an experiment in which the color difference varying with the film drawing rate was measured for the metallic-color paint substitute film 101 and a solid-color paint substitute film. The color difference used in the experiment is a color difference index in Hunter L a b color space and is computed by the Hunter L a b color difference equation that used to prevail from the early stages of application of the color difference evaluation technology to the paint industry. It is shown in FIG. 5 that the solid-color paint substitute film undergoes little change even if the film drawing rate rises, while the metallic-color paint substitute 101 represents increase in color difference in proportion to the increase of the film drawing rate.
Accordingly, when a metallic paint substitute film 101 is bonded, in particular, to an exterior component having a complex shape among various exterior components of an automobile or the like, the film 101 is drawn to a large extent, partly, especially at a convexly curved area, and thus the largely drawn convexly curved area has an appearance different in color from surrounding areas that are not drawn so much. For that reason, the metallic-color paint substitute film 101 can be applied only to a component having a simple shape. It would conversely turn out that paint substitute films applicable to the component having a complex shape as described above could disadvantageously be restricted to solid-color paint substitute films.
The present invention has been made in view of the above-discussed circumstances.